1. Field of the Invention
The invention relates to an apparatus for applying a decoration to at least one article using a tank which contains a liquid on which the decoration floats.
2. Description of Related Prior Art
U.S. Pat. No. 4,010,057, corresponding to German Patent No. DE-A-25 34 640, describes a method and apparatus for applying a decoration to an article using hydrostatic pressure. This patent is hereby incorporated by reference.
U.S. Pat. No. 4,348,246 and U.S. Pat. No. 4,388,866 describe transfer printing techniques in which the film with the decoration to be transferred is not placed upon a layer of water but instead is placed upon a layer of granules or a deformable layer of pins.
U.S. Pat. No. 4,436,571 describes a transfer printing technique in which the article to receive a decoration is immersed in a specific way into a flowing liquid with the decoration floating thereupon. The article is presented to the decoration in a continuous movement in the general direction of the liquid flow along a downward path oblique to the surface of the liquid and then along an upward path oblique to the surface of the liquid to provide contact between the decoration and the article. The article is immersed within a liquid in a zig-zag motion wherein the angle the article enters and exits the liquid is adjustable. With this known technique the decoration of an article having a relatively complex shape is very difficult and frequently entails trial and error tests which are costly.
U.S. Pat. No. 4,407,881, corresponding to German Patent DE-A-32 19 992, describes a transfer printing technique in which the decoration is supported on a layer of a special film made of a hydrophilic, deformable layer which can swell by absorption of water, and a further layer which is placed over the hydrophilic layer and is varyingly permeable to water so that the hydrophilic layer expands to a greater or lesser extent.
U.S. Pat. Nos. 4,229,239 and 4,269,650 describe another transfer printing technique in which the decoration is prepared before the transfer by a solvent in order that it detaches itself more easily from the supporting film when transferred onto the article. This activation of the decoration (printing pattern) takes place directly before transferring the film with the decoration to the surface of the water. The film supporting the decoration is water soluble so that, upon contact with the water, the film dissolves and the decoration is then floating on the surface of the water alone (without the film). The decoration is then transferred to the article to be decorated by subsequent immersion of the article. This technique utilizes a solvent in order to make the detachment of the decoration from the supporting film easier.
U.S. Pat. No. 4,231,829 describes a transfer printing technique in which boric acid or a salt thereof is added to the PVA film supporting the decoration on the liquid or to the water on which the decoration floats in order to promote the transfer process.
In prior art designs, the article to be decorated is moved along two dimensions in a main plane of movement. The main plane of movement is defined by two vectors; a vector corresponding to the direction of the flow of the liquid and a vector perpendicular (normal) to the surface of the liquid.
It is difficult to match the movement of the article during the immersion operation precisely to the flow speed of the liquid or to the movement of the decorative film floating on the liquid, and it is also difficult to adjust the expansion of the decoration on the liquid precisely in relation to the requirements of the article and its immersion movement. The prior art processes, in general, contain too many uncontrolled parameters which must be controlled to effectively transfer with precision a decoration onto an article.
U.S. patent application Ser. No. 08/966,811 filed Nov. 10, 1997 and titled "Method and Apparatus for Manipulating an Article for Applying a Decoration Thereon," discloses an apparatus which uses a robot to move and immerse an article to be decorated in such a way that its movement also has components transverse to a main plane of movement defined by a vector in the direction of flow of the water and a vector perpendicular to the surface of the water. The present invention also provides that the article to be decorated is moved during immersion in such a way that its movement has components transverse to its main plane of movement. In other words, the article is moved in three dimensions through the liquid rather than moved just in two dimensions.
One object of the present invention is to provide a decoration application apparatus capable of guiding a multiplicity of articles through the tank at a high throughput while maintaining high quality in the application of the decoration.